A known embodiment of a display device is a self-emitting display device such as an organic electroluminescent display device. Electroluminescence is shortened to “EL” hereafter. In organic EL display devices, light emitted from a light-emitting layer advances in all directions and some of the light is totally reflected due to a difference between the refractive index of the light-emitting element and the refractive index of external space (air). Much of the light totally reflected by the interface between the light-emitting element and the air is trapped within the light-emitting element and is not extracted to the external space. For example, if the refractive index of the light-emitting layer is 1.8, then out of the light emitted from the light-emitting layer, approximately 20% of the light is extracted to the external space from the light-emitting layer and the remaining 80% of the light is trapped in the light-emitting layer. Thus, conventional organic EL devices have a problem of light utilization efficiency being low.
PTL 1 below describes an organic EL display device including a support substrate, an organic EL element provided on the support substrate, and a light reflection layer reflecting light emitted by the organic EL element. In the light reflection layer, the organic EL display device is provided with concave parts including inclined faces along the outer edge of an organic light-emitting layer. Light emitted from the organic light-emitting layer is reflected by the inclined faces of the concave parts and then returns toward the organic EL element. It is stated that this configuration can prevent image quality degradation such as bleeding, and can improve light utilization efficiency